Adhesives are playing a progressively more important role in the production and maintenance portions of today's industry. As used herein, "adhesive" frequently refers not only to high strength bonding materials including rapid-fixturing structural adhesives, but also to related materials which serve primarily to seal or lock the joint between adjacent surfaces (such as threadlocking compounds for nuts and bolts) where comparatively low adhesion is adequate. One of the most important types of adhesives, particularly to the metal-working industry, is the class of anaerobic adhesives. These are adhesives which remain liquid in the presence of air (oxygen) but which polymerize upon the exclusion of air to form hard, durable resins with excellent adhesive properties. Since air is automatically excluded between mating surfaces of metal and other non-porous parts, these adhesives are particularly useful in applications involving non-porous materials.
As with other adhesive materials, anaerobics conventionally are applied in the liquid state to allow the adhesive to contact and "wet" the surfaces to be bonded.
Numerous United States patents have been issued on various anaerobic systems and aerobically-curing compositions. Frauenglass et al U.S. Pat. No. 3,757,828, Sept. 11, 1973 in column 4, lines 25-35, refers to several such patents, but none of these patents disclose or suggest the anaerobic compositions of the present invention.
Wegemund et al, U.S. Pat. No. 3,642,750, Feb. 15, 1972 discloses anaerobic adhesive or sealant compositions which comprise liquid polymerizable esters of acrylic acid or methacrylic acid with 5,6-dihydrodicyclopentadienol; see column 2, lines 23 to 25, in the general description of the invention starting in line 15 of column 2, Examples I through VI, and claim 1 (column 6, lines 41-49) of the patent. The acrylate or methacrylate of 5,6-dihydrodicyclopentadienol, when used to seal or adhere the mating threaded surfaces of a bolt-nut assemblage or the unthreaded mating surfaces of close-fitting bearing rings joined to a shaft therein, manifested improved stability to heat. However, anaerobic adhesive compositions containing the aforesaid acrylate or methacrylate, in spite of their relatively high boiling points, have an odor that is quite characteristic, pervasive, persistent, and objectionable under certain conditions when put into use by certain operative personnel. Furthermore, these esters form seals and bonds which are extremely hard and brittle and subject to rupture on shock unless mixed with other copolymerizable monomers which can serve to soften or toughen the seal.